If you use your screen to watch a ton of movies and the aspect ratio leaves you with black bars on the top and bottom, you’ll get burn in from the middle of the screen even if the middle has all dynamic images.

Even if you use the whole screen, say if a portion of the screen tends to use saturated color more than the rest of the screen, you’ll get burn in even if everything is non-static.

All burn in is is the uneven brightness of the screen due to the degradation of pixels. Having a static image is just the most common way for burn in to happen, NOT the only way.

https://www.rtings.com/tv/learn/real-life-oled-burn-in-test

> Update 05/31/2019: The TVs have been running for over 9000 hours (around five years at 5 hours every day). Uniformity issues have developed on the TVs displaying Football and FIFA 18 and are starting to develop on the TV displaying Live NBC. Our stance remains the same: we don't expect most people who watch varied content without static areas to experience burn-in issues with an OLED TV.

Even though it’s rare for your average consumer, dynamic images still can and will cause burn ins. And this test doesn’t take into account for black bars and someone displaying content that has more saturated content in one portion of the screen over the other (it does talk about how each sub pixels degrade at different speed though)